The invention concerns disposable dry cleansing articles formed from a melt extruded fibrous web that has incorporated into the fibers forming the web at a melt extruded lathering surfactant.
U.S. Pat. No. 4,578,414 describes wettable olefin polymer fibers. The fibers are formed from a composition comprising a polyolefin resin and one or more defined surface-active agents. Such agents may be present in an amount of from about 0.01 to about 5 percent by weight. The surface-active agents can be (1) an alkoxylated alkyl phenol in combination with a mixed mono-, di- and/or triglyceride; (2) or a polyoxyalkylene fatty acid ester; or (3) a combination of (2) with any part of (1). The preferred polyolefin is polyethylene, and all of the examples employed an ethylene/1-octene copolymer, the latter apparently being a minor component.
Disposable personal cleansing products have recently been proposed which use a lathering surfactant and optionally conditioners that are impregnated into a water insoluble substrate. This water insoluble substrate is typically a fibrous material such as a nonwoven fibrous web. An example of this execution is described in U.S. Pat. No. 6,063,397 which provides a combination of a lathering surfactant and a conditioner into a water insoluble substrate where the ratio of the surfactant to conditioner is less than 40:7. This product is dry as sold then wetted by the consumer and then disposed of after use. An earlier patent of the same genre proposes a lathering surfactant and an oil soluble conditioning agent at a ratio of less than 20:1, U.S. Pat. No. 5,972,361. This product is also dry as sold, wetted by the consumer and generally subsequently disposed of after a single use. U.S. Pat. No. 6,267,975 discloses a multilayer water insoluble substrate with the lathering surfactant and other ingredients located between the layers. The multiple layers have differing “Loft-Soft” ratios to enhance lathering. A wide variety of nonwoven type webs are described including air laid webs, meltblown webs, spunbond webs, carded webs and wet laid webs. In all these dry articles, the lathering surfactants are impregnated into the nonwoven web or the like by conventional coating techniques such as dip coating, slot coating or the like. Although effective for a single use, these coated webs however generally lose their effectiveness after a single use or rinsing.
Melt blown microfiber (BMF) webs are made by extruding a thermoplastic polymer or resin such as a polyolefin through a row of small, side-by-side orifices into a high velocity gaseous stream which attenuates the emerging resin into microfibers. The gaseous stream creates a turbulence which entangles the microfibers to form a coherent web that is deposited onto a collector such as a moving screen. It is known to make a BMF web hydrophilic by incorporating a surfactant into the web fiber by means of extruding a thermoplastic resin/surfactant premix. When the thermoplastic resin is polypropylene, an amount of surfactant exceeding 6% by weight of the resin may be required to maximize the hydrophilicity and absorbency properties of the web. More commonly, surfactant is topically applied, e.g., by being sprayed onto a finished BMF web, see U.S. Pat. Reissue No. 31,885 (Meitner) which concerns the use of BMF webs as articles or articles that can clean off both water and oil from a surface in a single pass.
U.S. Pat. No. 4,933,229 proposes a method to increase surfactant loading by use of a static mixer immediately prior to extruding the polymer. The resulting web has excellent wet web strength and is used as an absorbent article. The surfactant is not of the lathering type and the web is not usable as a cleansing article. In U.S. Pat. No. 4,578,414 (Sawyer et al.), the invention is characterized in that it “differs from the prior art by incorporating surface active agents directly into the bulk polymer resin rather than introducing a copolymer or applying a surface treatment to fabricated fibrous structures” (col. 6, 23–26). Sawyer goes on to say that preferred blends comprise about 95% to about 99.9% of the olefin polymer, the remainder being the surfactant.
U.S. Pat. No. 4,070,218 (Weber) concerns a spunbond nonwoven web which differs from a BMF web in that its fibers are substantially continuous and, as deposited, are substantially not fused together at crossing points. The Weber web is made from a mixture of a thermoplastic resin such as polypropylene and a surfactant (there called a “lubricating agent”). “Alternatively, the lubricating agent may be metered directly into extruder 12 if desired” (col. 2,57–59). Then after being calendered, “the bonded web 34 is heated to cause the lubricating agent to migrate to the fiber surfaces” (col. 4). Weber's surfactant has a molecular weight in the range of from 200 to 4000.
There is a need for a disposable dry lathering cleansing article that is capable of multiple uses or rinsings, for example, for use in personal care or home care.